Fig. 1: Crystal structure of YbMnBi₂, schematic Fermi surface, and experimental setups.

a The spins of Mn atoms in single crystal YbMnBi₂ are antiparallel within the ab plane, slightly canted along the [110] direction, and ferromagnetically stacked along the c axis. b Schematic depiction of the Fermi surface near the Weyl points. The Fermi surface is extremely elongated along the c direction, while the Fermi velocity (indicated by the color) is much larger in the ab plane. Note that this image is broadened in the \({{{{\boldsymbol{k}}}}}_{{{{\boldsymbol{x}}}}}\)-\({{{{\boldsymbol{k}}}}}_{{{{\boldsymbol{z}}}}}\) plane for visual clarity; the actual aspect ratio of the Fermi surface is closer to 200:1. c A schematic drawing of the experimental configuration of the Nernst effect measurement, in which magnetic field H was applied along the spin canting direction [110], heat flux j_Q was along \([1 \bar{1} 0]\), and recorded transverse voltage V was along [001]. d A schematic drawing of the experimental configuration of the thermal Hall measurement, in which magnetic field H was applied along the spin canting direction [110], heat flux j_Q was along \([1\bar{1}0]\), and the transverse temperature difference ∆_yT was obtained through the subtraction of the readouts of the two transverse thermometers, which is T₃ – T₂ in this setup. e A schematic drawing of the experimental setup of the electrical Hall experiment, in which external magnetic field H was along the spin canting direction [110], applied current flow I was along \([1 \bar{1} 0]\), and measured transverse voltage V was along [001]. f A schematic drawing of the experimental setup of a separate electrical transport experiment, in which external magnetic field H was along the spin canting direction [110], applied current flow I was along [001], and measured voltage V was also along [001].